The following prior art references are considered by applicants to be the most pertinent to the present invention:
[A] J. K. Wolf and G. Ungerboeck, "Trellis coding for partial-response channels", IEEE Trans. Comm., Vol. COM-34, No. 8, August 1986, pp. 765-773.
[B] T. A. Lee and C. Heegard, "An Inversion Technique for the Design of Binary Convolutional Codes for the 1-D.sup.N Channel", Proc. IEEE Regional Meeting, Johns Hopkins, February 1985.
[C] A. R. Calderbank, C. Heegard and T. A. Lee, "Binary convolutional codes with application to magnetic recording", IEEE Trans. Info. Th., Vol. IT-32, No. 6, November 1986, pp. 797-815.
[D] H. Thapar and A. Patel, "A Class of Partial Response Systems for Increasing Storage Density in Magnetic Recording", presented at Intermag 1987, Tokyo, Japan.
[E] R. Wood, "Viterbi Reception of Miller-Squared Code on a Tape Channel", Proceedings of IERE Video and Data Recording Conference, Southampton, England, 1982.
[F] K. Immink and G. Beenker, "Binary transmission codes with higher order spectral zeros at zero frequency", IEEE Trans. Info. Th., Vol. 33, No. 3, May 1987, pp. 452-454.
Reference [E] demonstrates the use of a simplified Viterbi detector in conjunction with the rate 1/2, Miller-squared code on a full response tape channel. The code has a spectral null at zero frequency, implying bounded accumulated charge, and the receiver operates with a degenerate state diagram which tracks only the accumulated charge. Coding gain arises from the fact that the code has minimum free Hamming distance 2, versus the minimum distance of 1 for uncoded binary data.
Reference [F] describes binary codes wherein both the code power spectral density and its low order derivatives vanish at zero frequency, and the minimum Hamming distance of a K-th order zero-disparity code is at least 2(K+1).
The techniques heretofore disclosed, including those in above-cited references [A], [B], [C], [E] and [F], do not teach the application of trellis codes with K-th order spectral zeros to enable high-rate reliable transmission on partial response channels. Nor do they describe methods for obtaining enhanced coding gain by exploiting the memory inherent in the partial response channel function.
There is a need for techniques which can provide high rate codes that improve upon those found in the prior art by enabling significantly reduced hardware requirements, particularly in the maximum-likelihood detector, for specified coding gains. In addition, such techniques should provide high rate codes with significant coding gains suitable for partial response channels, such as disclosed in reference [D], which are not addressed by the prior art techniques.